Method for producing film electrode jointed product and method for producing solid polymer type fuel cell

ABSTRACT

A method for producing a membrane electrode assembly  1  for solid polymer electrolyte fuel cell, the membrane electrode assembly  1  including a solid polymer electrolyte membrane  2  comprising an ion exchange membrane, a first electrode  3  having a first catalyst layer  31 , and a second electrode  4  having a second catalyst layer  41 , the first electrode  3  and the second electrode  4  being disposed so as to be opposed to each other via the ion exchange membrane, the method including: applying a coating solution containing a catalyst onto a base film  101  to form a first catalyst layer  31 ; applying a coating solution containing an ion exchange resin dissolved or dispersed in a liquid onto the first catalyst layer  31  to form an ion exchange membrane; then applying a coating solution containing a catalyst onto the ion exchange membrane to form a second catalyst layer  41 ; and finally, peeling off the base film  101  from a resulting laminate. According to this method, it is possible to produce membrane electrode assembly  1  for high-performance solid polymer electrolyte fuel cell having catalyst layers each having a uniform thickness efficiently and continuously.

TECHNICAL FIELD

The present invention relates to a method for producing a solid polymerelectrolyte fuel cell as well as to a method for producing a membraneelectrode assembly for solid polymer electrolyte fuel cell.

BACKGROUND ART

Hydrogen/oxygen fuel cells produce in principle only water as theirreaction product and hence receive attention as electric powergenerating systems that produce little adverse effect on the Earth'senvironment. Among them, solid polymer electrolyte fuel cells, inparticular, are greatly expected to come in practice since their powerdensity has been raised with rapid progress of study in recent years.

Conventionally, such a solid polymer electrolyte fuel cell usuallyoutputs power by the reaction between a fuel gas supplied to the anodeside and an oxidant gas containing oxygen to the cathode side,respectively, of a membrane electrode assembly in which gas-diffusiveelectrodes each provided with a catalyst layer containing a catalyst andan ion exchange membrane are joined with each other. The followingmethods, for example, are known as membrane electrode assemblyproduction methods.

-   (1) Method in which a catalyst is caused to deposit directly on an    ion exchange membrane (JP-B-58-47471).-   (2) Method in which gas-diffusive electrode sheets having a    catalytic activity are formed and the electrode sheets are joined    with an ion exchange membrane (U.S. Pat. No. 3,134,697, U.S. Pat.    No. 3,297,484, and JP-B-2-7398).-   (3) Method in which two sets (half cells) of an ion exchange    membrane and a catalyst layer formed thereon are formed and the two    sets are adhered by pressure to each other with their respective ion    exchange membrane sides facing each other to form a membrane    electrode assembly.

Recently, the method (2) has been mainly employed in view of its meritthat a small amount of a catalyst can be utilized effectively. Thefollowing processes, for example, have been proposed as specificprocesses for method (2). (2-1) Electrochemical deposition process (U.S.Pat. No. 5,084,144). (2-2) Process in which a coating solutioncontaining a catalyst is applied onto an ion exchange membrane, orprocess in which a catalyst layer is formed by applying a coatingsolution containing a catalyst onto a gas diffusion layer, that isdisposed adjacently to each catalyst layer to assist the catalyst layerin ensuring the stable gas-diffusibility thereof and to function also asa current collector, to obtain a electrode and two of the electrodes andan ion exchange membrane are joined together by means of a hot press orthe like (coating process, JP-A-4-162365). (2-3) Process in which acatalyst layer is formed on a separately-provided base film, thecatalyst layer is laminated with an ion exchange film, and the catalystlayer is transferred to the ion exchange membrane by hot-pressing(transfer process).

Also, method (3) has been tried since it has the merit of enabling thethickness of an ion exchange membrane to be reduced (JP-A-6-44984,JP-A-7-176317, and the like).

With the prior art transfer process noted above, however, it is requiredthat the hot-pressing transfer be performed under such a low-pressurecondition as not to crush a large number of fine pores which are presentin the catalyst layers in order to ensure the gas-permeability withinthe catalyst layers. It is, therefore, difficult to completely transferthe catalyst layers to the membrane, resulting in a low yield or a highprobability that the thickness of each catalyst layer becomesnon-uniform. For this reason, a problem arises that it is difficult toadjust (make uniform) the amount of the catalyst in the plane directionof the membrane electrode assembly, hence, to obtain stable cellperformance.

The coating process noted above conventionally employs a process ofapplying mainly a coating solution onto each gas diffusion layer inorder to ensure fine pores within the catalyst layer, improve thegas-permeability and prevent concentration polarization in a highcurrent density region. However, since such a gas diffusion layer isusually composed of porous carbon paper or carbon felt, a portion ofuneven surface of the gas diffusion layer sometimes bites into the ionexchange membrane when the gas diffusion layer is joined with the ionexchange membrane by means of a hot press. In this case, the thicknessof the ion exchange membrane partially varies and hence becomesnon-uniform, raising problems including a lowered open circuit voltagedue to gas leakage, short-circuit and the like. Thus, this process has adifficulty in stably producing membrane electrode assemblies using athin ion exchange membrane having a thickness of not more than 30 im,for example.

DISCLOSURE OF INVENTION

Accordingly, it is an object of the present invention to provide a novelproduction method which solves the foregoing problems of the prior artand is capable of efficiently and continuously producing ahigh-performance membrane electrode assembly for solid polymerelectrolyte fuel cell having catalyst layers with a uniform thickness.

The present invention provides a method for producing a membraneelectrode assembly for solid polymer electrolyte fuel cell, saidmembrane electrode assembly comprising a solid polymer electrolytemembrane composed of an ion exchange membrane, a first electrode havinga first catalyst layer, and a second electrode having a second catalystlayer, said first electrode and said second electrode being disposedadjacently to said solid polymer electrolyte membrane and opposed toeach other via said solid polymer electrolyte membrane, said methodcomprising the steps of:

a step A of applying a first coating solution containing a catalyst 1onto a base film to form a first catalyst layer;

a step B of applying a coating solution for forming an ion exchangemembrane containing an ion exchange resin dissolved or dispersed in someliquids onto said first catalyst layer to form an ion exchange membrane;

a step C of applying a second coating solution containing a catalyst 2onto said ion exchange membrane to form a second catalyst layer; and

a step D of peeling off said base film from a laminate comprising saidfirst catalyst layer, said ion exchange membrane and said secondcatalyst layer formed on said base film via said steps A to C.

According to the method of the present invention, an assembly of thecatalyst layers and the membrane laminated on the base film in the orderof the first catalyst layer, the ion exchange membrane and the secondcatalyst layer is formed by the steps A to C. At the step A, it ispreferable that after the application of the first coating solutioncontaining the catalyst 1, the liquid component (the dispersing medium)is removed by drying and, then, the process proceeds to the step B. Atthe step B, the coating solution for forming the ion exchange membraneis applied onto the first catalyst layer, and the liquid component isevaporated off from the coating layer thus applied to form the ionexchange membrane layer that becomes the solid polymer electrolytemembrane on the first catalyst layer. At this time, the ion exchangeresin contained in the coating solution for forming an ion exchangemembrane impregnates fine pores of the first catalyst layer andsolidifies thereby securely joining the first catalyst layer and the ionexchange membrane at their interfaces.

Though the thickness of the ion exchange membrane can be adjusted byselecting a concentration, some liquids (solvents or dispersing media)or the like of the coating solution for forming ion exchange membrane ormeans at the step B, the application and drying of the aforementionedcoating solution may be repeatedly performed until a predeterminedthickness is obtained if a thick ion exchange membrane is to be desired.

Subsequently, the second coating solution containing the catalyst 2 isapplied onto the aforementioned ion exchange membrane to form the secondcatalyst layer at the step C and, thereafter, the process proceeds tothe step D where the base film is peeled off from the aforementionedfirst catalyst layer. Though it is possible to perform the steps A to Dcontinuously in the order of A, B, C and D without any other interveningstep, the steps A to C preferably include respective drying stepssubsequent to the applications of respective coating solutions.

If drying is not performed at the step A and the process proceeds to thesubsequent step B, there is a possibility that the catalyst and ionexchange resin in the first catalyst layer are mixed with the coatingsolution for forming ion exchange membrane due to the influence of thesolvent used in that coating solution and, hence, the components of thefirst catalyst layer are mixed with those of the ion exchange membrane.As a result, the interface between the first catalyst layer and the ionexchange membrane becomes indefinite, thus incurring a possibility thatthe thickness of the first catalyst layer and that of the ion exchangemembrane may not be controlled and that the first catalyst layer and theion exchange membrane may not exhibit their own inherent functions. Alsoin the case where the process proceeds to the step C without performingdrying at the step B, there is a possibility that incidents similar tothose described above occur between the ion exchange membrane and thesecond catalyst layer. If the drying is not performed at the step C andthe process proceeds to the subsequent step D, it becomes difficult topeel off the base film.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view showing a preferred embodiment of a membraneelectrode assembly for solid polymer electrolyte fuel cell obtained bythe production method of the present invention.

FIG. 2 is a sectional view schematically showing the construction of afirst applicator for carrying out the present invention according to adie coater process.

FIG. 3 is a sectional view schematically showing the construction of asecond applicator for carrying out the present invention according tothe die coater process.

BEST MODE FOR CARRYING OUT THE INVENTION

Each of the first electrode and the second electrode in the presentinvention may comprise a catalyst layer alone but may be constituted ofa catalyst layer and a gas diffusion layer by disposing a gas diffusionlayer comprising carbon cloth, carbon paper or the like adjacently tothe catalyst layer. Here, the gas diffusion layer is a porous layerdisposed between the gas flow path and the catalyst layer and has thefunction of evenly and sufficiently supplying a gas to the catalystlayer while functioning also as a current collector. In this case, amembrane electrode assembly can be formed by sandwiching an assembly ofthe catalyst layers and the ion exchange membrane between two sheets ofsuch gas diffusion layers. It is noted that each catalyst layer and arespective gas diffusion layer may be bonded together by means of a hotpress or the like.

Outside the membrane electrode assembly, a separator with a grooveusually formed at a surface thereof that becomes a gas flow path isdisposed to form a solid polymer electrolyte fuel cell. If such membraneelectrode assemblies are stacked upon another via such a separator, asolid polymer electrolyte fuel cell of a stacked structure is obtained.In the case where the substantial flow path width of the gas flow pathin the separator is narrow enough (from about 0.05 to 0.5 mm, forexample), it is possible to diffuse and supply a gas to the catalystlayer sufficiently even in the absence of the aforementioned gasdiffusion layer.

Preferably, an electrically-conductive layer comprising, for example, anelectrically-conductive carbon material and a binding material ispresent between the gas diffusion layer and the catalyst layer. Thepresence of the electrically-conductive layer would make it possible toprotect the catalyst layer and the ion exchange membrane from the unevensurface of the carbon cloth or the carbon paper, hence, to prevent anelectrical short-circuit caused by the unevenness of the surface of thecarbon cloth or the carbon paper. Further, it is possible to prevent thecatalyst layer from becoming useless in the cell reaction due to thepenetration of the catalyst layer into the voids of the gas diffusionlayer.

The binding material used in this case preferably comprises awater-repellent polymer. When a solid polymer electrolyte fuel cell isoperated, the reaction: 1/2O₂+2H⁺+2e⁻→H₂O takes place at the cathode toproduce water. Usually, a wet gas is supplied to each electrode forpreventing the polymer electrolyte membrane from drying in order tomaintain the electrical conductivity of the membrane. For this reason,if a solid polymer electrolyte fuel cell is operated under theconditions of a low operating temperature and a high gas utilization,water vapor condenses to cause an electrode-occluding phenomenon(flooding) to occur, resulting in a possibility that the power output islowered due to lowered gas-diffusibility when the cell is operated for along time. Under such operating conditions, the presence of theaforementioned electrically-conductive layer makes it possible toinhibit flooding.

Usually, the aforementioned electrically-conductive layer has electricalconductivity so as not to lower the power output and is formed bytreating the surface of a base for a gas diffusion layer with a liquidcontaining a water-repellent polymer such as PTFE and carbon black, forexample. According to the method of the present invention, it ispossible to form such an electrically-conductive layer in the samemanner as in the case of the catalyst layer and the ion exchangemembrane. Specifically, the following process can be employed.

A coating solution for forming electrically-conductive layer is appliedonto the base to form a first electrically-conductive layer, then thesteps A, B and C are performed in this order, and further the coatingsolution is applied thereonto to form a second electrically-conductivelayer. Namely, an assembly can be formed by forming five layersconsisting of first electrically-conductive layer/first catalystlayer/ion exchange membrane/second catalyst layer/secondelectrically-conductive layer on the base in this order and, then,peeling off the base from the electrically conductive layer. In thiscase, the procedure of the step A is performed such that the applicationis made not directly onto the base but onto the firstelectrically-conductive layer formed on the base. It is possible thatsuch an electrically-conductive layer is formed on only one of the firstcatalyst layer side and the second catalyst layer side.

In the case where such an electrically-conductive layer is formed asdescribed above, the polymer serving as the binding material ispreferably a fluorine-contained polymer since it has a superiorcorrosion resistance as well as water repellency and, particularly, afluorine-contained polymer substantially free of any ion exchange groupthat is soluble in a solvent is preferable. A water-repellent polymersuch as PTFE that is insoluble in such a solvent needs to be used asdispersed in a dispersing medium in the preparation of a coatingsolution and, therefore, a dispersant such as a surfactant is requiredto disperse the polymer homogeneously. Here, the surfactant ishydrophilic and a sufficient water-repellent effect is not provided ifthe surfactant is present in the electrically-conductive water-repellentlayer and, therefore, the aforementioned coating solution usually needsto be heat-treated at a temperature not lower than 300° C. after theapplication thereof to remove the dispersant. However, since an ionexchange resin used as a solid polymer electrolyte usually has aheat-resistant temperature lower than 300° C., theelectrically-conductive water-repellent layer applied on the secondcatalyst layer cannot be heated to a temperature allowing removal of thedispersant even when it is subjected to such a heat treatment, resultingin a possibility that sufficient water repellency may not obtained.

On the other hand, the use of a fluorine-contained polymer that issoluble in a solvent does not require any dispersant for preparing thecoating solution and, hence, it is sufficient to disperse carbon black,for example, as an electrically-conductive material in a solution of thefluorine-contained polymer. Accordingly, as long as the temperature of aheat treatment performed after the application of the coating solutionis higher than the boiling point of the solvent in the above solution,it is possible to form an electrically-conductive layer comprising theforegoing fluorine-contained polymer and the electrically-conductivematerial, hence, obtain a sufficient water-repellent effect.

The aforementioned fluorine-contained polymer that is soluble in asolvent is preferably a polymer having a fluorine-contained aliphaticcyclic structure at the main chain. Such a polymer is hard tocrystallize because of the twist of the molecule attributed to themolecular structure thereof and is soluble in a fluorine-containedsolvent. Examples of such polymers include polymers containing apolymeric unit represented by any one of the formulae (1) to (4). Informula (1), R¹ is a fluorine atom or a trifluoromethyl group, a is aninteger from 0 to 5, b is an integer from 0 to 4, c is 0 or 1, and a+b+cis from 1 to 6; in formula (2), d, e and f are independently an integerfrom 0 to 5, and d+e+f is from 1 to 6; in formula (3), R² and R³ areindependently a fluorine atom or a trifluoromethyl group; and in formula(4), g is 1 or 2.

Solvents that are capable of dissolving these fluorine-containedpolymers are mostly fluorine-contained solvents. Examples of suchsolvents include perfluorobenzene, dichloropentafluoropropane,perfluoro(2-butyltetrahydrofuran) and the like. The concentration of asolution of the aforementioned fluorine-contained polymer is preferably0.01% to 50% by mass.

It should be noted that the aforementioned electrically-conductive layerneed not have water repellency in the case where there is no possibilityof flooding, such as the case where reaction gases to be supplied to thecell are dry or are not in a sufficiently wet state, the case where thecell is operated at a low current density, the case where the gasutilization is low, or the case where the operating temperature issufficiently high.

In the present invention, the solid polymer electrolyte fuel cell ispreferably constructed such that the first catalyst layer formed on thebase film serves as the catalyst layer of the anode while the secondcatalyst layer formed on the ion exchange membrane serves as thecatalyst layer of the cathode. Since the anode and cathode of a solidpolymer electrolyte fuel cell are usually supplied with a gas containinghydrogen and a gas containing oxygen, respectively, it is required inobtaining a high-performance cell that the catalyst layer of the anodebe excellent in gas-diffusibility with respect to hydrogen and that thecathode be excellent in gas-diffusibility with respect to oxygen.

Since the ion exchange resin constituting the ion exchange membraneimpregnates the fine pores of the first catalyst layer and solidifies atthe step B, the first catalyst layer is easy to become dense thoughhaving an advantage that the interface with the ion exchange membranecan be firmly joined. However, the ion exchange resin has a far higherpermeability to hydrogen than to oxygen and, hence, as far as the anodeis concerned, there arises no problem of lowered gas-permeability evenif the catalyst layer of the anode is impregnated with the ion exchangeresin and hence has a dense structure.

On the other hand, if the first catalyst layer is used as the catalystlayer of the cathode, oxygen, which has a lower permeability thanhydrogen, has to pass through the catalyst layer densely filled with theion exchange resin, so that concentration polarization is likely to takeplace due to the limited mass transfer rate of oxygen, resulting in apossibility that the current-voltage characteristics are deteriorated.That is, since the catalyst layer of the cathode needs to be maintainedporous while the catalyst layer of the anode need not have so high aporosity as the catalyst layer of the cathode, the use of the firstcatalyst layer as the anode according to the production method of thepresent invention allows the porosity of the cathode to be maintained,thereby making it possible to provide a high-performance solid polymerelectrolyte fuel cell.

The first catalyst layer and the second catalyst layer in the presentinvention, which contain the catalyst 1 and the catalyst 2 respectively,preferably contain an ion exchange resin in addition to the respectivecatalysts in order to enhance the cell characteristics of the fuel cell.Accordingly, it is preferable to use a coating solution in which acatalyst and an ion exchange resin are dispersed or dissolved as acoating solution for forming catalyst layers. The ion exchange resinused here is also capable of functioning as a binder for the catalystlayers. The ion exchange resin contained in the catalyst layers may bethe same as or different from the ion exchange resin forming the ionexchange membrane. As in the case of the ion exchange membrane, theapplication and drying of the coating solution may be repeated to attaina predetermined thickness when the thickness of a catalyst layer is tobe made larger.

In the present invention, though the catalyst 1 and the catalyst 2contained in respective catalyst layers may be the same or different,the catalyst 1 as well as the catalyst 2 is preferably a catalystsupporting a metal catalyst composed of platinum or a platinum alloy oncarbon. Carbon support preferably has a specific surface area of from 50to 1500 m²/g. Within this range, the metal catalyst is supported on thecarbon support with good dispersibility and stably exhibits a superioractivity in the electrode reaction for a long time. Platinum ispreferable as such a metal catalyst because it is highly active withrespect to the hydrogen oxidation reaction at the anode and the oxygenreduction reaction at the cathode in a solid polymer electrolyte fuelcell. In some cases, the use of a platinum alloy could make it possibleto impart the electrode catalyst with further stability and activity.

The aforementioned platinum alloy is preferably an alloy comprisingplatinum and one or more metals selected from the group consisting ofplatinum group metals other than platinum (ruthenium, rhodium,palladium, osmium, iridium), gold, silver, chrome, iron, titanium,manganese, cobalt, nickel, molybdenum, tungsten, aluminum, silicon, zincand tin, and may contain an intermetallic compound of platinum and ametal alloyed with platinum. Particularly in the case where the anode issupplied with a gas containing carbon monoxide, the use of an alloycomprising platinum and ruthenium in the anode is preferable because theactivity of the catalyst is stabilized.

Though the thickness of each catalyst layer and that of the ion exchangemembrane in the present invention are not particularly limited, it ispreferred that the thickness of the ion exchange membrane be not morethan 50 μm. If the thickness of the ion exchange membrane is more than50 μm, the concentration gradient of the amount of water vapor in theion exchange membrane, which is sandwiched between the anode and thecathode, is decreased so that the ion exchange membrane becomes easy todry and, when the ion exchange membrane dries, the proton conductivitylowers, resulting in a possibility that the cell characteristics islowered. Though the thinner ion exchange membrane is more preferablefrom the foregoing viewpoint, the thickness of the ion exchange membraneis preferably from 3 to 40 μm, more preferably from 5 to 30 μm since itis possible that too thin ion exchange membrane causes a short-circuitto occur.

From the viewpoint of facilitating the gas diffusion in the catalystlayers and improving the cell characteristics, the thickness of eachcatalyst layer is preferably not more than 20 μm, and more preferably,it is uniform. According to the production method of the presentinvention, it is possible to form a catalyst layer having a uniformthickness of not more than 20 μm. Though it is possible that the amountof the catalyst loading per unit area is decreased to lower the reactionactivity when the catalyst layer is made thin, the use of a supportedcatalyst supporting platinum or a platinum alloy as the catalyst at ahigh supporting rate makes it possible to maintain the reaction activityof the electrodes high without any shortage of the amount of catalysteven if the catalyst layer is thin. From the foregoing viewpoint, thethickness of each catalyst layer is preferably from 1 to 15 μm.

There is no particular limitation on processes for forming the ionexchange membrane and the catalyst layers. Examples of specificprocesses include batch processes such as a bar coater process, a spincoater process and a screen printing process, and continuous processessuch as a post-weighing process and a pre-weighing process. Thepost-weighting process is one in which a coating solution is applied inexcess and, thereafter, the coating solution thus applied is removed toattain a predetermined thickness. The pre-weighing process is one inwhich the coating solution is applied in an amount required to obtain apredetermined thickness.

Such post-weighing processes include an air doctor coater process, ablade coater process, a rod coater process, a knife coater process, asqueeze coater process, a impregnate coater process, a comber coaterprocess, and the like, while such pre-weighing processes include a diecoater process, a reverse roll coater process, a transfer roll coaterprocess, a gravure coater process, a kiss-roll coater process, a castcoater process, a spray coater process, a curtain coater process, acalender coater process, an extrusion coater process, and the like. Thescreen printing process and the die coater process are preferable informing a uniform ion exchange membrane on a catalyst layer and, whenthe production efficiency is taken into consideration, the continuousdie coater process is preferable.

Next, specific embodiments of methods for obtaining a membrane electrodeassembly by the continuous die coater process will be described withreference to drawings.

FIG. 1 is a sectional view showing a preferred embodiment of a membraneelectrode assembly 1 for solid polymer electrolyte fuel cell obtained bythe production method of the present invention. The membrane electrodeassembly 1 has a first electrode 3 and a second electrode 4 which aredisposed on opposite sides of a solid polymer electrolyte membrane 2.The first electrode 3 is composed of a first catalyst layer 31, anelectrically-conductive water-repellent layer 32 and a gas diffusionlayer 33, while the second electrode 4 is composed of a second catalystlayer 41, an electrically-conductive water-repellent layer 42 and a gasdiffusion layer 43.

FIG. 2 is a sectional view schematically showing the construction of afirst applicator for carrying out the present invention by the diecoater process. A base film 101 passes through a guide roll 102, supportrolls 103, 104, 105 and 106 and a guide roll 107 and is led to apost-process, for example, a heat-treatment process to be describedlater. Application heads 111, 112 and 113 are disposed between thesupport rolls 103, 104, 105 and 106, and the application heads 111, 112and 113 are pressed against the surface of the base film 101 to applyplural coating solutions onto the base film 101 sequentially. Byadjusting the pressing force of each application head, it is possible toadjust the tension of a portion to be coated. The application heads 111,112 and 113 are provided with respective slits 121, 122 and 123, whichare supplied with a first coating solution, a coating solution forforming an ion exchange membrane and a second coating solution,respectively.

In the case where drying is necessary after the application of the firstcoating solution and before the application of the coating solution forforming an ion exchange membrane, it is sufficient to install a dryingdevice between the application head 111 and the application head 112,and the first coating solution can be dried by performing hot airdrying, for example. Here, the positional relation between the foregoingdrying device and the support roll 104 is not particularly limited.Likewise, in the case where drying is necessary after the application ofthe coating solution for forming ion exchange membrane and before theapplication of the second coating solution, it is sufficient to installa drying device between the application head 112 and the applicationhead 113.

By the production using the aforementioned applicator, the firstcatalyst layer 31, the solid polymer electrolyte membrane 2 and thesecond catalyst layer 41 are stacked on the base film 101. An assemblycomprising the catalyst layers and the membrane is obtained by peelingoff the base film 101 from the first catalyst layer 31, and a membraneelectrode assembly 1 is obtained by disposing gas diffusion layers 33and 43 formed with respective electrically-conductive layers 32 and 42on opposite sides of the assembly. As described earlier, theelectrically-conductive layers may be formed continuously in the samemanner as with the catalyst layers and the like and, in such a case, itis sufficient to install other application heads between the guide roll102 and the support roll 103 and between the support roll 106 and theguide roll 107, respectively and to supply a coating solution forforming electrically-conductive layer from those application heads.

FIG. 3 is a sectional view schematically showing the construction of asecond applicator for carrying out the present invention by the diecoater process. In the same manner as FIG. 2, a base film 101 passesthrough a guide roll 102, support rolls 103 and 104 and a guide roll 107and is led to a post-process, for example, a heat-treatment process tobe described later. An application head 210 is disposed between thesupport rolls 103 and 104 and is pressed against the surface of the basefilm 101 to apply plural coating solutions onto the base film 101,intermittently. By adjusting the pressing force, it is possible toadjust the tension of a portion to be coated. Specifically, for example,it is sufficient to fit a screw thread (not shown) to the rear side ofthe application head 210 and adjust the pressing force by means of thisscrew thread.

The application head 210 is provided with slits 221, 222 and 223, whichare supplied with the first coating solution, the coating solution forforming an ion exchange membrane and the second coating solution,respectively. In the case where an electrically-conductive layer is tobe formed using this applicator, it is sufficient to increase the numberof slits of the application head 210 so that electrically-conductivelayers are formed at the lowermost layer and/or the uppermost layer.

In the present invention, it is possible to use any one of afluorine-contained ion exchange resin and a fluorine-free ion exchangeresin as each of the ion exchange resin forming the ion exchangemembrane and the ion exchange resin contained in the catalyst layers,and such an ion exchange resin may comprise either a single ion exchangeresin or a mixture of two or more ion exchange resins. The ion exchangeresins contained in the catalyst layers on the anode side and thecathode side may be the same or different.

From the viewpoint of durability, however, the ion exchange resincontained in the catalyst layers as well as the resin constituting theion exchange membrane preferably comprises a perfluorocarbon polymerhaving a sulfonic acid group. Particularly preferable is a copolymercomprising a repeating unit based on tetrafluoroethylene and a repeatingunit based on a perfluorovinyl compound having a sulfonic acid group.

The perfluorovinyl compounds are preferably those represented byCF₂=CF(OCF₂CX)_(m)O_(p)(CF₂)_(n)SO₃H, wherein X is a fluorine atom or atrifluoromethyl group, m is an integer from 0 to 3, n is an integer from1 to 12, and p is 0 or 1, particularly preferably a compound representedby any one of the formulae 5, 6 and 7. In the formulae 5 to 7, q is aninteger from 1 to 8, r is an integer from 1 to 8, and t is 2 or 3.CF₂=CFO(CF₂)_(q)SO₃H  (5)CF₂=CFOCF₂CF(CF₃)O(CF₂)_(r)SO₃H  (6)CF₂=CF(OCF₂CF(CF₃))O(CF₂)₂SO₃H  (7)

The ion-exchange capacity of the ion exchange resin constituting the ionexchange membrane and that of the ion exchange resin contained in thecatalyst layers are each preferably from 0.5 to 4.0 meq/g dry resin,particularly preferably from 0.7 to 2.0 meq/g dry resin. If theion-exchange capacity is too low, the ion conductivity of the ionexchange membrane and that of the catalyst layers are lowered.

If the ion-exchange capacity is too high, on the other hand, thestrength of the ion exchange membrane is weakened, while the moisturecontent of the catalyst layers becomes high. When the moisture contentof the catalyst layers becomes high, water produced by the reaction ofthe cell and water fed together with a fuel gas to promote the reactionare difficult to discharge to the outside of the catalyst layers and,hence, it is possible that such water is stored within the catalystlayers. As a result, a flooding phenomenon is possible to occur thatfine pores of the catalyst layers are occluded with water and, hence,the supply of fuel gas to the catalyst layers becomes difficult, causingthe voltage of generated power to lower.

The solvent contained in the coating solution for forming an ionexchange membrane is required to be capable of dissolving or favorablydispersing the ion exchange resin and, hence, preferable solvents differfrom ion exchange resins. This holds true for the coating solution forforming a catalyst layer if an ion exchange resin is contained in thecatalyst layers. The solvent may be either a single solvent or a mixedsolvent of two or more solvents. However, a low-boiling-point solventhaving a boiling point of not higher than 50° C. is not preferablebecause the composition of a coating solution varies due to evaporationof the low-boiling-point solvent before or at the time of theapplication of the coating solution, making it difficult to control thethickness of a coating layer.

In the case where a coating solution contains a perfluorocarbon polymerhaving a sulfonic acid group, alcohols or fluorine-contained solventsare preferably used. The followings are exemplified in concrete.

Such alcohols are preferably alcohols each having 1 to 4 carbon atoms inthe main chain thereof; for example, methyl alcohol, ethyl alcohol,n-propyl alcohol, isopropyl alcohol, tert-butyl alcohol and the like areusable. Mixing an alcohol with water makes it possible to enhance thesolubility of an ion exchange resin.

The following solvents can be mentioned as examples offluorine-contained solvents.

Hydrofluorocarbons such as 2H-perfluoropropane, 1H,4H-perfluorobutane,2H,3H-perfluoropentane, 3H,4H-perfluoro(2-methylpentane),2H,5H-perfluorohexane, and 3H-perfluoro(2-methylpentane).

Fluorocarbons such as perfluoro(1,2-dimethylcyclobutane),perfluorooctane, perfluoroheptane, and perfluorohexane.

Hydrochlorofluorocarbons such as 1,1-dichloro-1-fluoroethane,1,1,1-trifluoro-2,2-dichloroethane,3,3-dichloro-1,1,1,2,2-pentafluoropropane, and1,3-dichloro-1,1,2,2,3-pentafluoropropane.

Fluoroethers such as 1H,4H,4H-perfluoro(3-oxapentane) and3-methoxy-1,1,1,2,3,3-hexafluoropropane.

Fluorine-contained alcohols such as 2,2,2-trifluoroethanol,2,2,3,3,3-pentafluoro-1-propanol, and 1,1,1,3,3,3-hexafluoro-2-propanol.

In the case where a coating solution contains a fluorine-free ionexchange resin, N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO),methylene chloride, chloroform, carbon tetrachloride,1,1,1-trichloroethane, 1,1,2-trichloroethane, trichloroethylene, andtetrachloroethylene may be used.

The solid content concentration of the first coating solution, the solidcontent concentration of the coating solution for forming an ionexchange membrane and the solid content concentration of the secondcoating solution each can be appropriately selected according to thethickness of an intended catalyst layer or the thickness of an intendedion exchange membrane and are not particularly limited but arepreferably from 1% to 50% by mass each, particularly from 5% to 35% bymass each. If the solid content concentration is too low, there is apossibility that a crack is developed when a coating layer is dried. Ifthe solid content concentration is too high, on the other hand, thecoating solution has a high viscosity and, hence, there is a possibilitythat uniform application thereof cannot be achieved.

In the present invention, the base film has a role of maintaining theshape of each catalyst layer and needs to be insoluble in the firstcoating solution and to be unmeltable during drying of each coatingsolution. Specifically, films respectively comprising the followingmaterials are preferably used.

Fluorine-free polymers such as polyethylene terephthalate (hereinafterreferred to as PET), polyethylene, polypropylene (hereinafter referredto as PP), and polyimide. Fluoropolymers such aspolytetrafluoroethylene, ethylene/tetrafluoroethylene copolymer,ethylene/hexafluoropropylene copolymer,tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, andpolyvinylidene fluoride.

Since the base film is peeled off from the first catalyst layer at thestep D, it is required that the base film be moderately easy to bepeeled off from the first catalyst layer. When this point is taken intoconsideration, the base film preferably comprises a fluoropolymer. If afilm comprising a fluorine-free polymer is used, the use of such a filmthat is surface-treated with a silicone-type parting agent, afluorine-type parting agent or the like is preferable; for example, PETsurface-treated with a parting agent can be used preferably.

In the present invention, it is preferred that a heat treatment beperformed after the formation of the second catalyst layer (after thecompletion of the step C) in order to improve the adhesion strengthbetween the first catalyst layer on the base film and the ion exchangemembrane and between the second catalyst layer and the ion exchangemembrane, to enhance the strength of the ion exchange membrane itselfand the strength of the resin itself contained in the catalyst layers,and further to enhance the bond strength of the membrane electrodeassembly. Specifically, for example, any one of the following three heattreatment processes may be performed.

1) An oven heating process in which a laminate comprising the firstcatalyst layer, the ion exchange membrane and the second catalyst layerwhich are formed on the base film is heated in an oven at a temperaturenot lower than the softening temperature of the ion exchange membrane.

2) A hot pressing process in which the foregoing laminate is bonded bymeans of a hot press at a temperature not lower than the softeningtemperature of the ion exchange membrane.

3) A hot rolling process in which the foregoing laminate is bonded bymeans of a hot roll at a temperature not lower than the softeningtemperature of the ion exchange membrane.

To produce membrane electrode assemblies with good productionefficiency, it is preferred that the heat treatment process be performedcontinuously, and in this respect, it is preferred that the oven heatingprocess be performed not in a batch manner but in a continuous manner orthat the hot rolling process be performed. The oven heating process canbe carried out by keeping the laminate formed on the base film in anoven heated to a temperature not lower than the softening temperature ofthe ion exchange membrane for a predetermined time period. Thetemperature to which the oven is heated at this time is preferably from100 to 200° C., particularly from 120 to 180° C. The keeping time ispreferably from 3 minutes to 2 hours, particularly from 10 minutes toone hour. If the keeping time is too long or the temperature is toohigh, there is the possibility that the proton conductivity of the ionexchange resin contained in the catalyst layers or that of the ionexchange membrane lowers. On the other hand, if the keeping time is tooshort or the temperature is too low, there is the possibility that theadhesion strength is not sufficiently enhanced or the strength of theion exchange membrane is not enhanced.

The hot rolling process can be carried out by, for example, passing thelaminate between heated rolls. At this time, the roll temperature ispreferably from 50 to 200° C., particularly from 100 to 180° C. Thelinear pressure between the rolls is preferably from 5 to 100 kg/cm². Ifthe temperature is too high, there is the possibility that the ionexchange resin contained in the catalyst layers or the ion exchangemembrane melts, while if the temperature is too low, the bond strengthbetween the ion exchange membrane and the catalyst layers is difficultto enhance. If the linear pressure between the rolls is too high, it ispossible that fine pores within the catalyst layers are crushed, whileif it is too low, the adhesion strength between the catalyst layers andthe ion exchange membrane is difficult to enhance.

The foregoing heat treatment is preferably preformed under environmentwhich is isolated from oxygen. If the heat treatment is performed in anatmosphere where oxygen is present, there is the possibility that a partof the ion exchange resin contained in the catalyst layers or the resinforming the ion exchange resin denatures due to the oxidation reactionand the power output consequently lowered.

Here, methods for heat-treating the aforementioned laminate by isolatingoxygen include a method in which the laminate is heat-treated in aninert gas atmosphere such as nitrogen gas or argon gas, a method inwhich the laminate is heat-treated in vacuum, a method in whichgas-impermeable films are adhered tightly on opposite sides of thelaminate and then the laminate is heat-treated, and the like. What isreferred to as “gas-impermeable film” here is a film having a gaspermeability constant of not more than about 2×10⁻¹⁰m³·m/m²·s·MPa forexample. The gas-impermeable film may be one having a larger area thanthe membrane electrode assembly and substantially capable ofsufficiently reducing the amount of oxygen in air contacting theaforementioned laminate. It is possible to use as materials which areexemplified for the base film. Accordingly, in the case where the heattreatment is performed after the completion of the step C and before thestep D, a gas-impermeably film may be adhered tightly to the basefilm-free side of the laminate (the upper surface of the layer appliedlast) and then the heat treatment may be performed.

Next, the present invention will be described specifically by way ofexamples (Examples 1 to 4, 6 and 7) and a comparative example (Example5), which do not limit the present invention.

EXAMPLE 1

As a first coating solution for forming anode catalyst layer, a liquidhaving a solid content concentration of 10% by mass was prepared bymixing a copolymer (ion exchange capacity: 1.1 meq/g dry resin,hereinafter referred to as copolymer A) comprising a repeating unitbased on CF₂=CF₂ and a repeating unit based onCF₂=CFOCF₂CF(CF₃)OCF₂CF₂SO₃H and a platinum/ruthenium alloy(platinum:ruthenium=4:6 in mass ratio) supported carbon(carbon:alloy=1:1 in mass ratio) at a mass ratio of 5:9 homogeneouslywith ethanol. This first coating solution was applied onto a PET filmsurface-treated with a silicone-type parting agent by a die coaterprocess and then dried at 80° C. to form a first catalyst layer having athickness of 10 μm and a platinum/ruthenium loading amount of 0.29mg/cm².

Onto the first catalyst layer was applied a coating solution (coatingsolution for forming an ion exchange membrane) comprising 14% by mass ofthe copolymer A and ethanol as a solvent by the die coater process,followed by drying with an oven at 80° C. for 10 minutes to form an ionexchange membrane having a thickness of 30 μm. Further, onto the ionexchange membrane was applied a second coating solution for forming acathode catalyst layer having a solid content concentration of 13.7% bymass and comprising the copolymer A and a platinum-supported carbon(platinum:carbon=1:1 in mass ratio) at a mass ratio of 1:2 and ethanolas a solvent by the die coater process, followed by drying to form asecond catalyst layer having a thickness of 10 μm and a platinum loadingamount of 0.23 mg/cm². After this laminate was cut to 7 cm square, thePET film was peeled off from the first catalyst layer to obtain anassembly of the catalyst layers and electrode.

Two frame-shaped polyimide films each having a thickness of 20 μm and anouter size of 5.6 cm×7 cm with a central cutout of 5 cm square wereprovided, and the foregoing assembly was sandwiched between the twofilms so as to position in a central portion and bonded with the filmsusing a silicone-type adhesive.

Two sheets of carbon paper each having a thickness of about 300 μm, inwhich an electrically-conductive layer having a thickness of about 10 imcomprising carbon black (commercial name: VULCAN XC-72, produced byCabot Co.) and PTFE particles was formed at a surface thereof, wereprovided and used as gas diffusion layers. The aforementioned assemblywas sandwiched between these gas diffusion layers to obtain a membraneelectrode assembly. At this time, the electrically-conductive layerswere positioned to contact respective electrodes. The membrane electrodeassembly thus obtained was incorporated into a cell for measuring cellperformance in such a manner that the first catalyst layer and thesecond catalyst layer became the anode and the cathode, respectively, togive a solid polymer electrolyte fuel cell having an effective electrodearea of 25 cm². An electric power generating test of this cell wasconducted at a cell temperature of 80° C. by supplying hydrogen gas andair to the anode and the cathode, respectively. The cell voltage at eachvalue of current density resulting at this time is shown in Table 1. Itshould be noted that the unit of each value in Table 1 is mV.

EXAMPLE 2

A membrane electrode assembly was obtained in the same manner as inExample 1 except that the coating solution for forming an ion exchangemembrane was applied by the die coater process and the thickness of anion exchange membrane was made 15 μm. The membrane electrode assemblythus obtained was incorporated into a cell for measuring cellperformance in the same manner as in Example 1, and a test was conductedin the same manner as in Example 1. The results are shown in Table 1.

EXAMPLE 3

A membrane electrode assembly was obtained in the same manner as inExample 2 except that the coating solution for forming an ion exchangemembrane was applied once by the die coater process, followed by dryingnaturally for 10 minutes, the coating solution for forming an ionexchange membrane was applied again thereover, followed by drying withan oven, and the thickness of an ion exchange membrane was made 30 μm bysuch a two-time application. The membrane electrode assembly thusobtained was incorporated into a cell for measuring cell performance inthe same manner as in Example 1, and a test was conducted in the samemanner as in Example 1. The results are shown in Table 1.

EXAMPLE 4

After the formation of a first catalyst layer, an ion exchange membraneand a second catalyst layer on a PET film in the same manner as inExample 1, the resulting laminate was heat-treated with an oven at 120°C. for 30 minutes and then the PET film was peeled off from the firstcatalyst layer. A membrane electrode assembly was obtained in the samemanner as in Example 1 except that this heat treatment procedure wasperformed, and this assembly was incorporated into a cell for measuringcell performance to conduct a test in the same manner as in Example 1.The results are shown in Table 1.

EXAMPLE 5 Comparative Example

The first coating solution was applied onto one side of a basecomprising a 50 μm-thick PP film by the die coater process so that theadhered platinum/ruthenium amount was 0.29 mg/cm², followed by drying toform a first catalyst layer. Similarly, a second catalyst layer wasformed with the use of the second coating solution by applying thesecond coating solution onto one side of a base comprising a 50 μm-thickPP film that was separate from the aforementioned PP film by the diecoater process so that the adhered platinum/ruthenium amount was 0.23mg/cm² and then drying the solution applied.

The two sheets thus obtained were opposed to each other so that theirsurfaces formed with the respective catalyst layers faced inward, and anion exchange membrane comprising a sulfonic acid-type perfluorocarbonpolymer (commercial name: FLEMION HR, produced by Asahi Glass Co. Ltd.,ion exchange capacity: 1.1 meq/g dry resin, dry thickness: 30 im) as asolid polymer electrolyte membrane was sandwiched between the sheets,followed by hot pressing. The hot pressing conditions were set to 130°C., 3 MPa and 4 minutes, and after the hot pressing, the base sheets onthe anode side and the cathode side were peeled off from respectivecatalyst layers to transfer the catalyst layers to the membrane, thusobtaining an assembly comprising the catalyst layers and the membrane.

A membrane electrode assembly was formed in the same manner as inExample 1 except that the aforementioned assembly was used as anassembly comprising catalyst layers and a membrane, and this assemblywas incorporated into a cell for measuring cell performance to conduct atest in the same manner as in Example 1. The results are shown in Table1.

EXAMPLE 6

After the formation of a first catalyst layer, an ion exchange membraneand a second catalyst layer on a PET film, the resulting laminate wasplaced in an oven, and a heat treatment was performed at 120° C. for 30minutes after the inside of the oven was evacuated and then charged withnitrogen gas. Then, the PET film was peeled off from the first catalystlayer. A membrane electrode assembly was obtained in the same manner asin Example 1 except that this heat treatment procedure was performed,and this assembly was incorporated into a cell for measuring cellperformance to conduct a test in the same manner as in Example 1. Theresults are shown in Table 1.

EXAMPLE 7

A polymer (molecular weight: about 100,000) comprising a polymeric unitbased on perfluoro(3-butenyl vinyl ether) was dissolved in a mixedsolvent (mass ratio=1:1) of perfluoro(2-butyltetrahydrofuran) andperfluoro(tributylamine) so that the concentration of the solute was1.7% of the total mass of the solution. This solution was mixed withcarbon black (commercial name: VULCAN XC-72, produced by Cabot Co.) sothat the mass ratio between the aforementioned polymer and carbon blackwas 3:7, followed by sufficient stirring to obtain slurry.

The above slurry was applied onto a PET film identical with that used inExample 1 by the die coater process and then dried at 120° C. to form anelectrically-conductive layer having a thickness of 10 μm. Onto thiselectrically-conductive layer were formed a first catalyst layer, an ionexchange membrane and a second catalyst layer in the same manner as inExample 1. Further, the aforementioned slurry was again applied onto thesecond catalyst layer by the die coater process and then dried at 120°C. to form an electrically-conductive layer having a thickness of 10 μm.In turn, by peeling off the PET film from the electrically-conductivewater-repellent layer formed first, an assembly having a five-layeredstructure comprising electrically-conductive layer/first catalystlayer/ion exchange membrane/second catalystlayer/electrically-conductive layer was obtained.

Two frame-shaped polyimide films each having a thickness of 20 μm and anouter size of 5.6 cm×7 cm with a central cutout of 5 cm square wereprovided, and the foregoing assembly was sandwiched between the twofilms so as to position in a central portion and bonded with the filmsusing a silicone-type adhesive. Subsequently, two sheets of carbon papereach having a thickness of about 300 μm were provided as gas diffusionlayers, and the aforementioned assembly was sandwiched between these gasdiffusion layers to obtain a membrane electrode assembly. At this time,the electrically-conductive layers were positioned to contact respectiveelectrodes. The membrane electrode assembly thus obtained wasincorporated into a cell for measuring cell performance so that thefirst catalyst layer and the second catalyst layer became the anode andthe cathode, respectively to conduct a test in the same manner as inExample 1. The results are shown in Table 1.

TABLE 1 Current Density (A/cm²) 0 0.2 0.7 Example 1 960 752 582 Example2 939 765 644 Example 3 953 754 593 Example 4 953 721 565 Example 5 940740 580 Example 6 925 754 602 Example 7 958 745 581

INDUSTRIAL APPLICABILITY

According to the present invention, it is possible to produce threelayers comprising a first catalyst layer, an ion exchange membrane and asecond catalyst layer easily, efficiently and continuously bysequentially repeating application and drying of coating solutions.Further, since the present invention makes it possible to produce thecatalyst layers so that each layer has a uniform thickness even if it isthin as well as to enhance the bond strength between the catalyst layersand the ion exchange membrane, particularly between the first catalystlayer and the ion exchange membrane, the present invention is capable ofproviding a high-performance solid polymer electrolyte fuel cellcomprising a membrane electrode assembly that is excellent ingas-diffusibility and capable of maintaining a high power output stably.

1. A method for producing a membrane electrode assembly for solidpolymer electrolyte fuel cell, said membrane electrode assemblycomprising a solid polymer electrolyte membrane composed of an ionexchange membrane, a first electrode having a first catalyst layer, anda second electrode having a second catalyst layer, said first electrodeand said second electrode being disposed adjacently to said solidpolymer electrolyte membrane and opposed to each other via said solidpolymer electrolyte membrane, said method comprising the steps of: astep A of applying a first coating solution containing a catalyst 1 ontoa base film to form a first catalyst layer; a step B of applying acoating solution for forming an ion exchange membrane containing an ionexchange resin dissolved or dispersed in a liquid onto said firstcatalyst layer to form an ion exchange membrane; a step C of applying asecond coating solution containing a catalyst 2 onto said ion exchangemembrane to form a second catalyst layer; and a step D of peeling offsaid base film from a laminate comprising said first catalyst layer,said ion exchange membrane and said second catalyst layer formed on saidbase film via said steps A to C.
 2. The method for producing a membraneelectrode assembly in accordance with claim 1, wherein each of said stepA, said step B and said step C includes a procedure of drying arespective coating solution after the application thereof to remove aliquid component contained in said coating solution, said step A, saidstep B and said step C are performed continuously in that order.
 3. Themethod for producing a membrane electrode assembly in accordance withclaim 1 or 2, wherein: a coating solution containing anelectrically-conductive carbon material and a binding material isapplied onto said base film to form a first electrically-conductivelayer prior to said step A; said first coating solution is applied ontosaid first electrically-conductive layer at said step A; and after saidstep C, a coating solution containing an electrically-conductive carbonmaterial and a binding material is applied onto said second catalystlayer to form a second electrically-conductive layer.
 4. The method forproducing a membrane electrode assembly in accordance with claim 3,wherein said binding material is a fluorine-contained polymer which issoluble in a solvent substantially free of an ion exchange group.
 5. Themethod for producing a membrane electrode assembly in accordance withany one of claim 1 or 2, wherein said ion exchange resin contained insaid coating solution for forming an ion exchange membrane comprises aperfluorocarbon polymer having a sulfonic acid group.
 6. The method forproducing a membrane electrode assembly in accordance with any one ofclaim 1 or 2, wherein each of said catalyst 1 and said catalyst 2 is asupport catalyst supporting a metal catalyst on carbon, said metalcatalyst being composed of platinum or a platinum alloy, and said firstcoating solution and said second coating solution contain aperfluorocarbon polymer having a sulfonic acid group.
 7. The method forproducing a membrane electrode assembly in accordance with any one ofclaim 1 or 2, wherein each of said first catalyst layer and said secondcatalyst layer is formed to have a thickness of not more than 20 μm, andsaid ion exchange membrane is formed to have a thickness of from 3 to 40μm.
 8. The method for producing a membrane electrode assembly inaccordance with any one of claim 1 or 2, wherein after said step C, theresulting laminate is subjected to a heat treatment.
 9. The method forproducing a membrane electrode assembly in accordance with claim 8,wherein said heat treatment is performed in an atmosphere isolated fromoxygen.
 10. The method for producing a membrane electrode assembly inaccordance with any one of claim 1 or 2, wherein said first electrode isused as an anode, and said second electrode is used as a cathode.
 11. Amethod for producing a solid polymer electrolyte fuel cell comprising amembrane electrode assembly, said membrane electrode assembly comprisinga solid polymer electrolyte membrane composed of an ion exchangemembrane, a first electrode having a first catalyst layer, and a secondelectrode having a second catalyst layer, said first electrode and saidsecond electrode being disposed adjacently to said solid polymerelectrolyte membrane and opposed to each other via said solid polymerelectrolyte membrane, said method comprising the steps of: a step A ofapplying a first coating solution containing a catalyst 1 onto a basefilm to form a first catalyst layer; a step B of applying a coatingsolution for forming an ion exchange membrane containing an ion exchangeresin dissolved or dispersed in a liquid onto said first catalyst layerto form an ion exchange membrane; a step C of applying a second coatingsolution containing a catalyst 2 onto said ion exchange membrane to forma second catalyst layer; and a step D of peeling off said base film froma laminate comprising said first catalyst layer, said ion exchangemembrane and said second catalyst layer formed on said base film viasaid steps A to C.
 12. The method for producing a solid polymerelectrolyte fuel cell in accordance with claim 11, wherein each of saidcatalyst 1 and said catalyst 2 is a support catalyst supporting a metalcatalyst on carbon, said metal catalyst being composed of platinum or aplatinum alloy, and said coating solution for forming ion exchangemembrane, said first coating solution and said second coating solutioncontain a perfluorocarbon polymer having a sulfonic acid group.
 13. Themethod for producing a solid polymer electrolyte fuel cell in accordancewith claim 11 or 12, wherein: a coating solution containing anelectrically-conductive carbon material and a binding material isapplied onto said base film to form a first electrically-conductivelayer prior to said step A; said first coating solution is applied ontosaid first electrically-conductive layer at said step A; and after saidstep C, a coating solution containing an electrically-conductive carbonmaterial and a binding material is applied onto said second catalystlayer to form a second electrically-conductive layer.
 14. The method forproducing a solid polymer electrolyte fuel cell in accordance with anyone of claim 11 or 12, wherein after said step C, the resulting laminateis subjected to a heat treatment.
 15. The method for producing a solidpolymer electrolyte fuel cell in-accordance with any one of claim 11 or12, wherein said first electrode is used as an anode, and said secondelectrode is used as a cathode.